形成 (xíngchéng) means 'to form, to take shape' and is used for abstract or natural processes (ice forming, opinions forming, a spirit forming). It contrasts with 塑造 (sùzào), which is more deliberate — molding a physical object or crafting an image/character — and with 成型 (chéngxíng), which focuses on a final, fixed shape after a process.